1. Field of the Invention
The present invention relates to a turbo compressor, and more particularly, to a turbo compressor for compressing air by using an impeller driven by a high speed motor.
2. Description of the Related Art
In general, there are several types of compressors, for example, piston compressors, rotor compressors and turbo compressors. In a turbo compressor, air is compressed by an impeller connected to a rotation shaft of a motor which rotates at a high speed. The turbo compressor may pose a stability problem because it has a complicated driving mechanism for the impeller and the bearings supporting the impeller are exposed to the conditions of high speed, heavy parts, and heat. For example, a typical turbo compressor uses a gear system to transfer power to the impeller.
FIG. 1 is a schematic view showing the structure of a conventional turbo compressor. Referring to the drawing, the turbo compressor includes a low-speed motor (not shown) for supplying power for rotation, a gear system 8 installed to convert the low speed rotational power to a high speed rotational power, a first impeller 1 provided for compressing air in the first phase, a first volute housing 2 for containing the air compressed by the first impeller 1, a second impeller 3 for compressing the air in a second phase, a second volute housing 4 for containing the air compressed by the second impeller 3, a bearing 5 for supporting a rotation shaft shared by the first and second impellers 1 and 3, respectively, a third impeller 6 for compressing the air in the third phase, and a third volute housing 7 for containing the air compressed by the third impeller 6. A cooling apparatus (not shown) for cooling the air compressed by the respective impellers may be installed to cool the compressed air at each step.
The conventional turbo compressor typically uses the gear system 8 as described above. The gears of gear system 8 commonly pose several problems and disadvantages, such as, since gears are heavy and voluminous, they require huge installation space should and increase the total weight of the compressor. In addition, the continuous motion of various parts of the gears generate low frequency vibrations and undesirable noise. Furthermore, the gear system requires periodic maintenance, including lubricating and controlling temperature of the various parts of the gear system, including a tilting pad bearing or ball bearing for supporting the rotation shaft. Therefore, a complicated system is necessary for providing an appropriate lubricating system and control of temperature. In particular, the turbo compressor needs a complicated sealing system for preventing intrusion of lubricant into the impeller.
When a motor for driving an impeller in a conventional turbo compressor is driven by electric power, the motor requires a starting current that is three or four times higher than regular current. Thus, the compressor needs a larger power equipment for the driving motor, which increases cost and requires bigger installation space. Also, since the maximum capacity of the driving motor is obtained at a particular frequency of the power, for example, 50 or 60 Hz, the whole system must be designed according to the frequency of the power.
Therefore, there is a need for a turbo compressor which has a simplified system and improved efficiency.
The advantages and purposes of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The advantages and purposes of the invention will be realized and attained by the elements and combinations particularly pointed out in the appended claims.
To attain the advantages and consistent with the principles of the invention, as embodied and broadly described herein, one aspect of the invention is a turbo compressor, comprising a motor having a rotation shaft rotatable at a high speed, a first impeller installed at one and portion of the rotation shaft for primarily compressing outside air, and a first volute housing for containing the air compressed by the first impeller. The compressor also comprises an intercooler having an inlet portion and an outlet portion, the inlet portion being installed adjacent the first volute housing for cooling the air compressed by the first impeller, a second impeller installed at the other and portion of the rotation shaft for secondarily compressing the air flowing from the intercooler, and a second volute housing for containing the air compressed by the second impeller. The compressor further includes a duct connecting the outlet portion of the intercooler to an inlet portion of the second impeller.
Consistent with the principles of the present invention, other aspects of the invention include the following. The rotation shaft of the motor may be supported by at least one air foil bearing. The motor may be controlled by an inverter module. The air supplied to the air foil hearings is supplied from the second volute housing. The air supplied to the air foil bearings is supplied by an external pressing apparatus. The air foil bearings comprise a housing, and a plurality of air foils installed at an inner surface of the housing for supporting the rotation shaft of the motor with a fluid film of the compressed air.
Further consistent with the principles of the present invention, the air foil bearings have a structure utilizing a flexible multi-leaf type foil which characteristically provides a large amount of play to misalignment inside a large motor. Since multiple shoots of foils are overlapped, the multi-leaf type foil bearing exhibits strong resistance against vibrations or impacts. Further, when coating of a surface of the foil is damaged, the effect on performance of the bearing can be reduced.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention as claimed. Additional advantages will be set forth in the description which follows, and in part will be understood from the description, or may be learned by practice of the invention. The advantages and purposes may be obtained by means of the combinations set forth in the attached claims.